Today I conducted several additional tests to determine if I could get Ubuntu to work with the combination of my Latitude D820, docking station, and Dell flat panel connected through the docking station with a DVI-D cable.
First I tried all of the video settings in the BIOS one at time and in various combinations. No joy nothing worked. Then I tried connecting via VGA cable and with various BIOS settings, again, nothing worked. Then I tried connecting the VGA cable directly to the back of the laptop with negative results. The GUI utility for using multiple screens did not detect the external screen and neither did xrandr -q when run from a terminal.
My conclusion is that there is no meaningful support provided by Ubuntu for running an externally connected monitor with my hardware configuration.